The present invention relates to automatic systems for monitoring and tracking product manufacturing.
In the modem era, product recalls, liability lawsuits, and warranty claims are an unfortunate but common part of the life of a manufacturing company. Even the best managed manufacturing operations are subject to producing defective merchandise requiring recalls. Furthermore, liability lawsuits and warranty claims may be made whether there is or is not a defect underlying the claim.
In this environment, it is critical to the profitability of a manufacturing organization, to improve quality control and minimize defects. Furthermore, since defects and claims asserting defects are to some extent unavoidable, it is critical to collect data on a manufacturing operation. When a defect occurs, such data will permit a subsequent determination of the cause of the defects and identification of specific lots, batches or individual manufactured products subject to these defects, so that recalls can be narrowly targeted and not over-inclusive. When a claim asserting a defect is made, such data can be used as evidence to refute allegations that improper manufacturing practices created a defect and/or to statistically prove that an acceptable number on defects exist within all manufactured parts.
In the past, computerized systems have been incorporated into manufacturing environments to address some of the concerns identified above.
For example, Cipelletti, U.S. Pat. No. 5,673,194 discloses a computer system for an electronics manufacturing environment in which circuit boards, having been previously assigned identifiers, are tracked through assembly workstations. The times at which the boards pass through the workstations are collected, as is data on the workstation operator, or its current operative parameters. This data can be later assembled, using time as an index, to determine the full manufacturing history of any one or group of circuit boards.
Nagaoka, U.S. Pat. No. 5,586,038, at col. 3, lines 55-67, describes an automobile manufacturing environment in which the serial numbers of parts assembled to a vehicle and the serial number of the vehicle frame are collected and stored as the parts are assembled to the vehicle. Manufacturing parameters such as torques applied in assembly of the part to the vehicle, are also collected and related to the serial number of the vehicle. Other systems for collecting and tracking manufacturing data are also known. Bennett, U.S. Pat. No. 4,591,983 discloses a database for storing configuration information for custom-assembled computer systems, including identifying parts and subassemblies of parts assembled into the computer systems. The assignee of the present patent application markets software and hardware systems for collecting and storing environmental data from a manufacturing environment each time a manufacturing machine cycles. A software product sold by Wonderware, known as Intrack, is a database for resource tracking and management for manufacturing environments, primarily intended for tracking and predicting the availability of supplies and inventory. In Intrack, typically batches of inventory or supplies are provided with identifiers and bar-coded. As these batches pass through the manufacturing system, the bar codes are scanned and the Intrack software maintains an updated record of the status of each batch, from which reports and predictions can be made.
The foregoing systems suffer from several difficulties. First, the approaches of Cipelletti and Nagaoka assume that the manufacturing process will begin with a substrate (Cipelletti) or framework (Nagaoka) which can be subsequently identified and to which all of the parts will be assembled. That is, the circuits made by Cipelletti in all cases include a circuit board, and the identifier for this circuit board is visible in the final product. Similarly, the vehicles made by Nagaoka in all cases include a frame and the frame""s identifier is visible in the final product. Unfortunately, this is not always the case. Some manufactured products do not have a underlying substrate or framework to which other parts are assembled. Furthermore, in some manufactured products the identifiers for some or all of the parts are permanently hidden when the parts are assembled. In each case, it would be impractical to use the Cipelletti/Nagaoka approach.
Another difficulty with the Cipelletti/Nagaoka systems is that tracking and identification are performed only at the level of the final assembly. Presumably, other systems are relied upon to identify defects which may occur in the manufacture of subassemblies assembled onto the final assembly tracked by Cipelletti or Nagaoka. This can lead to substantial difficulties. Specifically, inaccuracy in the tracking of the subassemblies can substantially undermine the cost effectiveness of the system. For example, if a part manufacturer determines that defects may have occurred in any of the parts manufactured over a four-week period, but cannot more narrowly identify the defective parts, all of the assemblies produced using those parts must be recalled or inspected, at a potentially substantial cost. While the Cipelletti or Nagaoka system can accurately determine which final assemblies must be recalled, they can do nothing to identify the cause of defects in the subassemblies or narrow the number of subassemblies, and therefore the number of final assemblies, that must be recalled or inspected.
A third difficulty with the systems described thus far, is that they have no facility for monitoring manual assembly steps or attempting to compensate for human error in manual assembly. Several known systems have been directed specifically to manual assembly steps, with varied success. Ahmed, U.S. Pat. No 4,819,176 describes a shrimp cleaning and packaging environment in which a computer system tracks the weight of batches or sub-batches of raw shrimp and cleaned shrimp, and the employees involved in cleaning those batches or sub-batches. Street et al., U.S. Pat. No. 5,781,443 and Kunik et al., U.S. Pat. No 4,821,197 disclose manual assembly stations, having bins for storing parts to be used in manual assembly. A computer system generates displays over each bin to indicate the parts to be used, and sensors in the bins detect when parts have been retrieved from the bins.
Ahmed, Street et al. and Kunik et al., while aiding manual assembly and improving the tracking of manual assembly steps, fall short of ensuring that manual assembly is being performed correctly. Specifically, the Ahmed system is capable only of identifying when a manual shrimp cleaning operation is producing excessive waste, but not in verifying that the operation is being correctly performed. The Street et al. and Kunik et al systems, while assisting manual assembly of components, do not truly verify that the appropriate parts are being used in manual assembly or that all of the required parts are being used, since the sensors coupled to the bins could be xe2x80x9cfooledxe2x80x9d, e.g., by a placing a hand into a bin without removing a part. Furthermore, none of Ahmed, Street et al. or Kunik et al provide facilities for tracking individual manual operations so that the parts used in the operation and the resulting assembly, and the identity of the assembler, can be cross-referenced.
The present invention overcomes these and other difficulties in the prior art, by providing a comprehensive manufacturing and tracking system. A system in accordance with the present invention is appropriate for any kind of assembly made by any kind manufacturing operation, including those which do not have or use a later-identifiable substrate or frame. In accordance with the present invention, tracking extends both to final assemblies as well as subassemblies used in forming final assemblies made from those subassemblies. Systems in accordance with the present invention are appropriate for use with both automated and manual assembly stations, and not only assist in manual assembly procedures but also verify that the appropriate parts are being used, in the proper order, in a manual assembly step.
In accordance with a first aspect, the invention features a computerized system for tracking the activities of a manufacturing system, the manufacturing system performing a manufacturing process in which an assembly is assembled from parts, at least some of the parts being assembled into a subassembly in a first manufacturing step prior to combining the subassembly with additional parts in a second manufacturing step. The invention can also be applied to single-step manufacturing environments, but this aspect of the invention is primarily applicable to multi-step manufacturing environments. Identifiers for parts, subassemblies or assemblies produced or used by the first and second manufacturing steps are stored and generated by a data processing system. The data processing system is responsive to the first and second manufacturing steps to produce and store identifiers for subassemblies produced in the first manufacturing step in synchrony with completion of the subassemblies by the first manufacturing step, and produce and store identifiers for assemblies produced in the second manufacturing step in synchrony with completion of the assemblies by the second manufacturing step. The resulting multi-level tracking of assembly steps and the subassemblies and assemblies produced by them, facilitates detailed tracking and reconstruction of the manufacturing process for an individual final assembly.
In another aspect, the invention features a computerized system for tracking the activities of a manufacturing system, in which a data processing system, upon receipt of a part identifier from an indicia reading system, retrieves from a data storage system, manufacturing step data for the manufacturing step, and verifies that the part associated with the read identifier is supposed to be used in the manufacturing step. If not, a warning can be generated, preventing inappropriate completion of a manufacturing step, particularly in manual assembly environments.
In a further aspect, the invention features a computerized system for tracking the activities of a manufacturing system, in which a data processing system determines that an assembly has been produced by a manufacturing step, when identifiers for all required parts identified in manufacturing data for the process step, have been read and verified. This facilitates manual assembly environments in particular, by ensuring that an identifier is generated for each part assembled, without requiring manual verification of the assembly of the part.
In an additional aspect, the invention features a computerized system for tracking the activities of a manufacturing system, in which a data processing system has sensors attached to the manufacturing system for detecting cycles of the manufacturing system indicative of completion of a manufacturing step, and generates an identifier for an assembly produced by the manufacturing step upon detection of completion of the manufacturing step, and stores the identifier. This analogously facilitates automated assembly, by ensuring an identifier is generated for each part that is made by a machine.
In specific embodiments of the invention, a bar code printer coupled to the data processing system prints a bar code when the data processing system produces an identifier for an assembly or subassembly. The bar code is printed on a sticker, which can then be either automatically or manually transferred onto the assembly or subassembly for which the identifier was generated. When a part or subassembly is used in a manufacturing step, a bar code reader reads the bar code from the part or subassembly, and delivers the identifier reflected in the bar code to the data processing system. In alternative embodiments, the bar code or other indicia can be scribed on the part, e.g. by a laser scribing system.
The data processing system, upon receipt of a series of identifiers from scanned bar codes, may evaluate whether identifiers for parts or subassemblies, were received in an order in which the parts or subassemblies are supposed to be used in the given manufacturing step, and if not, issue a warning. This further ensures that manual assembly procedures in particular are being correctly performed.
When the data processing system receives an identifier for a subassembly being combined into an assembly, the data processing system stores into the data storage system, an association between an identifier generated for the first subassembly to an identifier generated for the first assembly. This accumulated data facilitates later retrieval of the identifiers for individual component parts that are incorporated into an assembly.
The data processing system also includes sensors attached to the manufacturing system for collecting process condition measurements relating to performance of manufacturing steps. The data processing system associates these measurements with the identifier of the assembly or subassembly produced during performance of the manufacturing step.
The data processing system may also include a user interface for obtaining inspection information relating to the manufacturing system. The data processing system stores inspection information relating the manufacturing system""s performance of a manufacturing step, associated with an identifier generated for an assembly or subassembly produced during performance of the manufacturing step.
The data processing system can use the rate of generation of identifiers for assemblies or subassemblies produced during performance of a manufacturing step, to forecast future availability of assemblies or subassemblies produced by the manufacturing step based on the determined rate. This analogously facilitates production monitoring for automatic and manual assembly operations.
In accordance with further aspects, the invention features methods carried out by the computer systems described above.
The above and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.